Numerical Investigation of the Formation Mechanism and Control Strategy of Center Segregation in Continuously Casting Slab

Abstract

Slab center segregation occurs due to fluid flow in the continuous casting process, and is caused by shell bulging, thermal shrinkage, and so on. Their influences on center segregation evolution have been investigated separately in the past, whereas the combined effect is rarely reported. In this work, both shell bulging and thermal shrinkage on center segregation formation are studied. Accordingly, the control strategy of mechanical reduction to improve center segregation is analyzed. The results show that solid phase moves outward and inward periodically with shell bulging, which promotes the transport of rejected solute to the slab center. Near solidification end, solid phase still moves outward with thermal shrinkage, and the concentrated liquid is pushed out and flows to center part. Therefore, the transport behaviors with shell bulging and thermal shrinkage are completely different, and center segregation will be worse when both are considered. As solid phase is compressed by mechanical reduction, enriched liquid transported downward is suppressed and center segregation is reduced. With a greater reduction amount allocated in the later stage, center segregation can be obviously improved. Furthermore, the control strategy of mechanical reduction is to alleviate the relative movement between liquid and solid near the solidification end.

Multiphase Solidification Modeling of Solidification Structure Evolution and Macrosegregation of Round Bloom Continuous Casting Process with Mold Electromagnetic Stirring and Final Electromagnetic Stirring

“…[31,32] Compared with the ingot cast, many complicated multiscale macro/microscopic transport phenomena occurs in the continuous casting process and the caster length (from meniscus to torch cutting point) is usually larger than 20 m. Thus, the application of the volumeaveraged multiphase model in continuous casting process faces a big challenge of huge calculation resource and time. Luckily, Zhu and his coworkers [33][34][35][36] proposed that a volume-averaged columnar-equiaxed multiphase solidification model coupled a modified Gaussian heterogeneous nucleation law to treat the grain nucleation on the steady state of continuous casting process to investigate the macrosegregation and solidification structure in the continuous casting strand, and effects of electromagnetic stirring and mechanical reduction on the macrosegregation were also studied.…”